A differential data transmitter with pre-emphasis comprises a main driver coupled to receive an input data stream and to produce a main differential output stream which varies with the input stream, circuitry which provides a delayed and inverted version of the input stream, and a first pre-emphasis driver coupled to the output of the circuitry and arranged to produce a pre-emphasis differential output stream which varies with the delayed and inverted input stream. The pre-emphasis differential output stream is coupled to the main differential output stream to produce differential data transmitter output signals. The main and pre-emphasis drivers operate in parallel, with the pre-emphasis driver boosting the output signals when consecutive bits in the input stream change state, and attenuating the output signals when consecutive bits in the input stream do not change state.